Changing an objects origin just changes its location
Changing the origin point wont move the object, it changes where the object is "attached to".

Lets say you wanted to pick up a cup, you can pick it up by the handle, you can pick it up by the tip, you can pick it up by lots of ways. Wherever your skin touches the cup, thats the "origin point".

What are you trying to do with the grass? You can upload the .blend here
http://blend-exchange.giantcowfilms.com/